Incandescent electric lamps and fluorescent lamps are widely used as light sources for illumination devices.
In addition to these lamps, illumination devices using a semiconductor light-emitting element such as a LED or an organic EL (OLED) as a light source have been developed and used in recent years.
Since a variety of emission colors can be obtained with those semiconductor light-emitting elements, the development and use of illumination devices in which a plurality of semiconductor light-emitting elements with different emission colors are combined and the emission colors thereof are combined to obtain the radiated light of the desired color have been started.
Non-Patent Document 1 describes a fluorescent lamp which uses a narrow-band phosphor and which irradiates meat, fresh fish, or the like that are being sold at a grocery store. Patent Document 1 describes a fluorescent lamp as an alternative to a high-chroma high-pressure sodium lamp. Patent Document 2 describes a fluorescent light which is adjusted to form a spectrum having superior color rendering properties in all colors. Patent Document 3 describes a white semiconductor light-emitting device having superior color rendering properties in all colors (in particular, a color rendering property regarding vivid red).
Patent Document 1: Japanese Patent Application Laid-open No. H10-255722
Patent Document 2: Japanese Patent Application Laid-open No. 2002-198009
Patent Document 3: WO2011/024818
Non-Patent Document 1: “General-purpose fluorescent light Meat-kun”, [online], Prince Electric Co., LTD., [retrieved on May 16, 2011], Internet <URL: http://www.prince-d.co.jp/pdct/docs/pdf/catalog_pdf/fl_nrb_ca2011.pdf>
However, careful consideration by the present inventors have revealed that the fluorescent lamp described in Non-Patent Document 1 has a wavelength region where an emission line of mercury used is present and a wavelength region with insufficient emission intensity as shown in a spectral energy distribution chart and that there may be cases where a difference in chroma of light between the two wavelength regions is significant. In particular, when irradiating light to a monochrome irradiated subject, a problem exists in that the irradiated subject cannot be vividly presented if a peak wavelength of a reflectance spectrum of the irradiated subject is within a range of the wavelength region with insufficient emission intensity.
In addition, the spectral energy distribution chart in Non-Patent Document 1 shows that overall chroma is low in a wavelength region of visible light. In particular, chroma is found to be low regarding vivid red, vivid green, and vivid blue.
As illustrated in the spectral distribution charts shown in FIGS. 1 and 3 of Patent Document 1, the fluorescent lamp described in Patent Document 1 has a wavelength region where an emission line of mercury used is present and a wavelength region with insufficient emission intensity. Therefore, in a similar manner to the fluorescent lamp described in Non-Patent Document 1, there is a problem in that some irradiated subjects cannot be vividly presented.
Patent Documents 2 and 3 do not describe, and do not even suggest, increasing chroma. Moreover, since Patent Document 2 does not describe a spectrum of light emitted by the fluorescent light according to the invention, the chroma of the fluorescent light cannot be analyzed.